Add the beginnings of a loudness range meter.

[nageru] / lrameter.cpp

diff --git a/lrameter.cpp b/lrameter.cpp
new file mode 100644 (file)
index 0000000..79a702d
--- /dev/null
+++ b/lrameter.cpp
@@ -0,0 +1,87 @@
+#include <QPainter>
+
+#include "lrameter.h"
+
+using namespace std;
+
+namespace {
+
+int lufs_to_pos(float level_lu, int height)
+{
+       const float min_level = 9.0f;    // y=0 is top of screen, so “min” is the loudest level.
+       const float max_level = -18.0f;
+       int y = lrintf(height * (level_lu - min_level) / (max_level - min_level));
+       y = std::max(y, 0);
+       y = std::min(y, height - 1);
+       return y;
+}
+
+}  // namespace
+
+LRAMeter::LRAMeter(QWidget *parent)
+       : QWidget(parent)
+{
+}
+
+void LRAMeter::paintEvent(QPaintEvent *event)
+{
+       QPainter painter(this);
+       const int margin = 5;
+
+       painter.fillRect(0, 0, width(), height(), parentWidget()->palette().window());
+       painter.fillRect(margin, 0, width() - 2 * margin, height(), Qt::black);
+
+       // TODO: QLinearGradient is not gamma-correct; we might want to correct for that.
+       QLinearGradient on(0, 0, 0, height());
+        on.setColorAt(0.0f, QColor(255, 0, 0));
+        on.setColorAt(0.5f, QColor(255, 255, 0));
+        on.setColorAt(1.0f, QColor(0, 255, 0));
+       QColor off(80, 80, 80);
+
+       float level_lufs;
+       {
+               unique_lock<mutex> lock(level_mutex);
+               level_lufs = this->level_lufs;
+       }
+
+       float level_lu = level_lufs + 23.0f;
+       int y = lufs_to_pos(level_lu, height());
+
+       // Draw bars colored up until the level, then gray from there.
+       for (int level = -18; level < 9; ++level) {
+               int min_y = lufs_to_pos(level + 1.0f, height()) + 1;
+               int max_y = lufs_to_pos(level, height()) - 1;
+
+               if (y > max_y) {
+                       painter.fillRect(margin, min_y, width() - 2 * margin, max_y - min_y, off);
+               } else if (y < min_y) {
+                       painter.fillRect(margin, min_y, width() - 2 * margin, max_y - min_y, on);
+               } else {
+                       painter.fillRect(margin, min_y, width() - 2 * margin, y - min_y, off);
+                       painter.fillRect(margin, y, width() - 2 * margin, max_y - y, on);
+               }
+       }
+
+       // Draw the target area (+/-1 LU is allowed EBU range).
+       int min_y = lufs_to_pos(1.0f, height());
+       int max_y = lufs_to_pos(-1.0f, height());
+
+       // FIXME: This outlining isn't so pretty.
+       {
+               QPen pen(Qt::black);
+               pen.setWidth(5);
+               painter.setPen(pen);
+               painter.drawRect(2, min_y, width() - 5, max_y - min_y);
+       }
+       {
+               QPen pen;
+               if (level_lu >= -1.0f && level_lu <= 1.0f) {
+                       pen.setColor(Qt::green);
+               } else {
+                       pen.setColor(Qt::red);
+               }
+               pen.setWidth(3);
+               painter.setPen(pen);
+               painter.drawRect(2, min_y, width() - 5, max_y - min_y);
+       }
+}